Here you go. Create 2 onChnage client scripts and a script include. The following code assumes the u_dur_1, u_du_2,u_dur_3 as the three duration field names.
OnChange script on u_dur_1 field
function onChange(control, oldValue, newValue, isLoading, isTemplate) {
if (isLoading || newValue === '') {
return;
}
if(g_form.getValue('u_dur_2')!=''){
var ga = new GlideAjax('CalculateDuration');
ga.addParam('sysparm_name','durationCalulator');
ga.addParam('sysparm_dur1',newValue);
ga.addParam('sysparm_dur2',g_form.getValue('u_dur_2'));
ga.getXML(CallBack);
}
function CallBack(response) {
var answer = response.responseXML.documentElement.getAttribute("answer");
g_form.setValue('u_dur_3',answer);
}
}
OnChange client script on u_dur_2 field:
function onChange(control, oldValue, newValue, isLoading, isTemplate) {
if (isLoading || newValue === '') {
return;
}
if(g_form.getValue('u_dur_1')!=''){
var ga = new GlideAjax('CalculateDuration');
ga.addParam('sysparm_name','durationCalulator');
ga.addParam('sysparm_dur2',newValue);
ga.addParam('sysparm_dur1',g_form.getValue('u_dur_1'));
ga.getXML(CallBack);
}
function CallBack(response) {
var answer = response.responseXML.documentElement.getAttribute("answer");
g_form.setValue('u_dur_3',answer);
}
}
Script include:
Name:CalculateDuration
client callable:true
Script:
var CalculateDuration = Class.create();
CalculateDuration.prototype = Object.extendsObject(AbstractAjaxProcessor, {
durationCalulator: function(){
var duration = new GlideDuration(this.getParameter('sysparm_dur1') );
var duration2 = new GlideDuration(this.getParameter('sysparm_dur2') );
var answer = duration.subtract(duration2);
return answer.getDurationValue();
},
type: 'CalculateDuration'
});
